1. Field of the Invention
The present invention relates to a phase current estimation apparatus for a motor and a magnetic pole position estimation apparatus for a motor.
The priority is claimed on Japanese Patent Application No. 2008-291090, filed Nov. 13, 2008, the content of which are incorporated herein by reference.
2. Description of the Related Art
In the related art, for example, there is disclosed an inverter apparatus that outputs two first and second reference voltage vector components, of which phases are different by 60 degrees and from which a command voltage vector can be generated, in a first time interval of one PWM period (one period of a carrier wave) and outputs two third and fourth reference voltage vector components, of which phases are different by 180 degrees with respect to the first and second reference voltage vector components in a second time interval of one PWM period consecutively following the first time interval so as to secure a desired length of a pulse width in the case where a degree of modulation is small or in the case where a phase of an output voltage vector is approximate to a phase of a single reference voltage vector (refer to, for example, Japanese Unexamined Patent Application Publication No. 2005-12934).
However, in the inverter apparatus in the related art, there are problems in that only two-phase modulation is an effective modulation scheme, in that it is difficult to cope with the change in the modulation scheme, and in that it is not possible to improve the general versatility. In addition, since only one phase current can be detected in the one PWM period, a plurality of the PWM periods are needed in order to estimate three phase currents. Therefore, there is a problem in that the estimation cannot be promptly performed. In addition, since harmonic components (that is, the differences between the vectors obtained by the decomposition and the command voltage vector) corresponding to one PWM, which are generated by decomposing the command voltage vector into two vectors in the PWM periods of two first and second time intervals for securing a desired length of a pulse width are not quantitatively analyzed by using mathematical equations, there is a problem in that it is not possible to improve the estimation accuracy of the phase currents by controlling the harmonic components.
The present invention is contrived by taking into consideration the above problems, and an object of the present invention is to provide a phase current estimation apparatus for a motor capable of suitably improving estimation accuracy of a phase current and a magnetic pole position estimation apparatus for a motor capable of suitably improving the estimation accuracy of a magnetic pole position.